[Uniformity] Lateral Shift


A tire must be rotating to generate a lateral force.  As in the radial force diagram, once equilibrium is established for the inflated, loaded, and rotating tire, the lateral force variation becomes periodic.


The average value of this force is called Lateral Shift; the variation is called Lateral Force Variation.


Lateral Shift Variation will change significantly when the direction of rotation is changed. A positive lateral shift in the clockwise direction, (1st  DIR.), will become a negative lateral shift in the counterclockwise direction (2nd DIR.).


Today tires could wind up in service in either direction of rotation; therefore they must meet the specifications in both directions of travel.
Lateral Force Variation